High Sensitivity Electromagnetic Testing of Hi-Tech and Safety Critical Metal Components
Lead Research Organisation:
University of Warwick
Department Name: Physics
Abstract
This 4 year PhD iCASE project will undertake research into new methods of inducing high frequency currents into metal components to test them for small surface defects and cracks (<0.5mm long) - beyond the limits of what is currently viable. The University of Warwick has developed some new instrumentation that is capable of inducing currents (eddy currents) in the surface of a metal sample such as titanium, at frequencies over 15MHz - far beyond what is available at the moment. We do this using specially designed coils that are positioned close to the sample, but do not touch the sample, and then using the magnetic field arising from these currents to determine if there are changes in the electromagnetic properties of the sample, that could be caused by material degradation or small cracks. The presence of even the smallest cracks on components such as jet engine turbine blades could be catastrophic due to the high stresses and temperatures that these components can be exposed to. This project will provide the PhD student the chance to apply and develop their knowledge of the underlying physics to a real world problem, working on equipment and analysis that will improve safety and produce some novel new measurement techniques.
The project will work closely with academic and industrial members of the EPSRC funded Research Centre for NDE.
The project will work closely with academic and industrial members of the EPSRC funded Research Centre for NDE.
People |
ORCID iD |
| Steven Dixon (Primary Supervisor) | |
| Amanda To (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/P510695/1 | 01/10/2016 | 31/12/2021 | |||
| 1917436 | Studentship | EP/P510695/1 | 25/09/2017 | 24/09/2021 | Amanda To |
| Description | Eddy current testing is widely used to inspect safety-critical components, where it is important to find surface-breaking defects and fatigue cracks at their earliest stage of growth. This requires finding sub-millimetre length defects, which usually means the electromagnetic skin depth of the eddy current must be <1 mm. To achieve skin depths of <1 mm on low conductivity metals such as Ti and TiAl, the frequency of the excitation current needs to be greater than several MHz. Eddy current sensor frequencies of up to 40 MHz, providing a good signal to noise have been achieved by situating circuitry directly behind the coils. As an alternative, lower frequency (<1MHz) parametric approaches have been investigated, where magnitude and phase of the eddy current signal are independently measured. Our work is effectively a combination of these two approaches, operating at frequencies above 1 MHz and locating the sensor electronics behind the coils, whilst simultaneously measuring magnitude and phase of the eddy current signal. Even when locating the electronics close to the coils, increasing frequency will always lead to an increase in electrical noise as stray capacitances become more significant. We have found that our approach can improve sensitivity to defects in experimental 2D scans of the sample surface. We expanded on earlier work by changing various parameters such as defect orientation and the lift-off of the eddy current coils. Through this, it was found that our new approach can improve stand-off performance and the ability to measure defects close to the edge of a sample. Experimental results, in addition to some finite element modelling, was collected to support these findings. |
| Exploitation Route | The research may be used to help improve the capability of eddy current sensors to find small defects on safety-critical metal components. |
| Sectors | Aerospace, Defence and Marine,Energy |